INFANTS DETECTION OF SHEARING MOTION IN RANDOM-DOT DISPLAYS

Random-dot kinematograms were used to estimate infants' thresholds for shearing motion in the absence of flicker and position cues. The principal advantage of these stimuli is that changes in dot position are camouflaged by the presence of numerous matching dots, thus necessitating the detection of motion before the extraction of lor-al pattern features. Thirteen- and 20-week-old infants were tested with a forced-choice preferential looking technique. The target stimulus resembled a vertically oriented corrugated pattern that oscillated at 1 Hz, if, and only if, shearing motion was detected. Infants were tested at different velocities, ranging from 0.7-degrees/s to 5.6-degrees/s, and the results revealed minimum velocity thresholds of 3.5-degrees/s and 1.2-degrees/s for 13- and 20-week-old infants, respectively. Possible interpretations for these results based on position- or flicker-sensitive mechanisms are considered and are found inconsistent with the overall pattern of results. It is concluded that infants detect shearing motion in random-dot displays with a motion-sensitive mechanism.